Door lock having security device

Abstract

An improvement of the door lock which is extensively used in all kinds of doors is disclosed which is characterized in that a security device is added to the existing door lock without modifying the constitution and the operating principle of the existing door lock, so that, once the security device is activated from the inside of the room, the door lock can never be opened by even the corresponding key and other means from the outside, thereby protecting the persons staying inside the room from the attempt of an unpermitted intruder.

What is claimed is: 
     
       1. In a door knob latch set having a locking mechanism of the push knob variety, including: an outer handle, said outer handle being coupled with an outer rotating tube and an inner rotating tube, said outer rotating tube and said inner rotating tube having arcuate projections projecting from the end opposite said outer handle, and said inner rotating tube having an elastic support plate covering said end opposite said outer handle;   an inner handle having a push knob centrally disposed therethrough, said push knob being attached to a first end of a shaft, said shaft passing through a movable pipe and having at a second end a first leading end and a second leading end; and   a cylinder, said cylinder having therethrough a latch elastically supported by a spring, said latch being connected at one end with a lower portion of a runner, said runner being coupled at an upper portion with a lock plate, said runner being coupled on a first side with said outer rotating tube, and said runner being coupled on a second side opposite said first side with said movable pipe;   THE IMPROVEMENT WHEREIN said lock plate is provided with at least one insertion slot, said arcuate projections of said inner rotating tube and said outer rotating tube being respectively provided with a centrally located insertion slot; and a security device being provided, said security device including a locking plate having a first integral locking pin and a second integral locking pin, two circular rods coupled with said locking plate, two springs installed on said circular rods, and a spring washer installed to the ends of said circular rods, said security device being inserted into said movable pipe adjacent to said inner handle, said security device having a knob projecting out from said inner handle and around said push knob, whereby said security device may be manipulated back and forth into said moveable pipe.   
     
     
       2. An improved door knob latch set in accordance with claim 1, further comprising a latching rod linked with said lock plate, and wherein said first locking pin has a leading end and a lower end, whereby engaging said security device by pushing said security device knob causes said leading end of said first locking pin to engage with said at least one insertion slots of said arcuate projections, and whereby said lower end of said first locking pin prevents the elevation of said latching rod. 
     
     
       3. An improved door knob latch set in accordance with claim 1, wherein said movable pipe is provided with a latching slot, and said security device knob is provided with a latching protuberance, said latching protuberance engaging said latching slot when said security device knob is pushed and turned clockwise, thereby securing the whole security device in the engaged position. 
     
     
       4. An improved door knob latch set in accordance with claim 1, wherein said second integral locking pin engages said insertion slot of said lock plate, thereby immobilizing said lock plate. 
     
     
       5. An improved door knob latch set in accordance with claim 1, said door lock having a push knob with a protuberance formed on an outer surface of said push knob, said protuberance being coupled with a slot formed in said security device knob, whereby said security device is disabled when said push knob is pushed in. 
     
     
       6. An improved door knob latch set in accordance with cm 1, wherein said locking plate, said washer, and said spring washer are provided with slots, said slots receiving said shaft when said security device is installed within said movable pipe.